This invention is in the field of phenolic molding compounds, and particularly in the fields of the newer phenolic molding technologies, such as sheet molding compound (SMC), pultrusion, filament winding and continuous laminating processes, as well as in ram injection molding and transfer molding.
Phenol-formaldehyde resins have long been mixed with fillers and used in phenolic molding compositions, which because of their thermosetting characteristics can be readily cured into hard, durable molded products. Such a phenolic molding composition is disclosed in U.S. Pat. No. 2,424,787. This patent discloses the use of both "one-stage" or resole and "two-stage" or novolak resins in the production of phenolic molding compositions. In the production of the resole resin molding compositions, the patentee discloses that it is necessary to mix the resin syrup with the filler, because of the liquid nature of the resin. The patentee discloses that in accordance with a preferred embodiment of the invention an alkali metal or an alkaline earth metal oxide including compounds of calcium and magnesium is incorporated in the molding composition with the phenolic resin and filler. Magnesium oxide is mentioned as particularly advantageous. The addition of the oxide to the molding composition causes the composition to harden at room temperature or at slightly elevated temperatures. However, this solidification does not convert the resin into the final infusible, insoluble stage and the solidified product may be easily molded under heat and pressure to form a satisfactory molded product.
Philipps in U.S. Pat. No. 4,075,155 of Owens-Corning Fiberglas Corporation, extended the use of phenol formaldehyde resole molding compositions to sheet molding compound (SMC) technology which heretofore have been generally limited to the use of polyester resins. Philipps discloses molding compositions that included fillers, compounds such as calcium hydroxide and magnesium hydroxide, mold release agents and coupling agents.
Another patent filed by Owens-Corning Fiberglas Corporation, U.S. Pat. No. 3,956,227, discloses phenolic molding compounds including cement which contains calcium oxide and further disclosed the use of silane coupling agents. Sheet molding compounds were disclosed by the patentees. Related patents include U.S. Pat. Nos. 3,944,515 and 3,988,289. A later patent U.S. Pat. No. 4,182,701, was directed to phenolic molding compounds made by mixing the phenol and aldehyde reactants together with calcium hydroxide and a silane coupling agent. Use of calcium hydroxide and magnesium hydroxide during the reaction of the phenolic resin is also disclosed in U.S. Pat. No. 4,070,331.
In the same period, Olivo et al in U.S. Pat. No. 4,116,921 disclose phenolic molding compounds made from formaldehyde and bisphenol. The patentees disclose the use of calcium oxide or hydroxide in the molding compounds. These patentees also disclose the use of hollow carbon and hollow phenolic resin microballoons.
Another approach to making phenolic sheet molding compounds is disclosed in British patent No. 1,363,227 to Farkas. The patent discloses sheet molding compounds made from a phenol aldehyde resole resin that is modified with a glycol. The resins are cured with acids. Resins that are modified with oligomers are disclosed in U.S. Pat. No. 4,419,400.
There are several patent applications published in Japan, dealing with this technology. In a Dainippon application published as Sho-No. 56-92927, sheet molding compounds are disclosed which contain resole phenolic resins, calcium and/or magnesium hydroxides or oxides and fillers such as talc, clay and the like. The use of a silane coupling agent is not disclosed and the working examples are limited in scope to the use of calcium hydroxide and aluminum trihydrate as the principal filler.
In Japanese Patent Publication Sho-No. 58-91935 (also Dainippon), phenolic molding compounds which contain resole phenolic resins, a thickener, such as the oxides or hydroxides of calcium and magnesium, fillers and reinforcing materials are combined with abrasive materials for use in brake shoes. Sheet molding compound technology is used in forming the brake shoes.
In Sumitomo Bakelite Japanese Publication Sho-No. 59-170126, sheet molding compounds made with resole phenolic resins, alkaline earth metal oxides or hydroxides are impregnated into special configurations of continuous and discontinuous glass fibers.
Despite these disclosures in the literature, there remains the fact that no truly commercially attractive base catalyzed phenolic resin sheet molding compound has been put on the market and used to any extent.
Accordingly, it is an object to this invention to provide commercially attractive sheet molding compositions made from phenolic resole resins, and also to provide novel technology that can be employed advantageously in some of the newer molding techniques including sheet molding compound, pultrusion, filament winding and continuous laminating processes.